Patients often require continuous or bolus administration of medications which can be delivered at regularly occurring times, times dictated by a treatment regimen, in response to a patient's request, or in response to a biological/physiological event. An increasing assortment of implantable drug delivery systems are being designed to treat patients who may use the drug delivery technology to dispense therapeutic agents to treat medical conditions such as diabetes, arthritis, cancer, movement disorders such as spasticity, heart conditions and irregularities, various neurological or psychiatric conditions, disorders of the digestive system, autoimmune disorders, and many other medical conditions and disorders as well. The medical drug delivery technology can be used for a wide variety of medical, veterinary, pharmaceutical and research purposes, can be totally or partially implantable or, if small enough, can be ingestible.
Implantable osmostic pumps have been known for some time (e.g., U.S. Pat. No. 4,588,394). The more recent generation of implantable drug delivery systems can deliver two or more substances (e.g., U.S. Pat. No. 3,449,983), at controlled rates of delivery (e.g., U.S. Pat. No. 5,240,713). U.S. application 60/284,771 (the '771 application) and provisional Ser. No. 10/099,060 (the '060 application) provide for a programmable implantable pump system with several reservoirs and a multiple lumen catheter. The '711 application provides for bolus drug delivery over a short period of time, for delivering multiple substances independently at programmed rates of delivery to one or more regions, and for drug delivery based upon physiological need. However, mixing of different drugs between reservoirs is not addressed.
The '711 patent application discloses a multiple lumen catheter for delivering multiple substances to a specific site by using concentrically embedded lumen. This technique causes the diameter of the outer lumen of the catheter to increase, requiring more material, and creating a catheter which may not bend easily, and which may be more difficult to use when treating certain disorders, such as those of the central nervous system, where a smaller diameter catheter may be advantageous. A further disadvantage is that the internal lumen can break and be undetected. Further, when the diameter of a multiple lumen catheter grows beyond a certain limit, the amount of substance which is chronically held in the outer lumen may become great, thus depleting the amount of that substance which is in the pump and ready for delivery, and also increasing the probability of unwanted leakage. Further, having several multi-lumen catheters necessitates a considerable amount of substance, compared to a small diameter catheter.
U.S. provisional application Ser. No. 10/251,941 discloses a drug delivery system which contains a series of chambers which may each hold a different drug, each of which can be sent to different catheters. The '941 also contains an accumulator chamber between the reservoirs and the catheter, which is provided to hold drug overflow. While drugs may be mixed in the '941 application, this occurs by breaching the drug chambers themselves so that 100% of the drugs in those chambers become mixed.
Mixing of drugs can be important in order to produce therapeutic effects. For example, in chemotherapy, some of the drugs should not be mixed until immediately prior to use. Some drugs may potentiate the effects of other drugs, such as Sufentanil and Clonidine as described in U.S. Pat. No. 6,471,688 (the '688 patent), incorporated by reference herein. The '688 patent feeds two drugs to the same catheter, and can be designed to keep them from mixing until they reach the intended delivery site by using a dual, rather than a single, lumen catheter. In this embodiment the timing of the mixing is related to the rate of drug delivery. One disadvantage with this system is if a drug is to be delivered rapidly, but the desired mixing is to occur slowly or prior to delivery, the invention of the '688 patent would not achieve the desired drug mixing during the drug delivery.
U.S. Pat. No. 5,980,508 describes a system that allows for multiple drugs, multiple doses, and continuous or pulsatile/interval delivery. However, the technology is sub-optimal because the concentration and delivery system must be configured prior to the implantation of the pump, rather than being dynamically adjusted once implanted, based upon the needs of the patient.
U.S. Pat. No. 4,588,394 (the ‘394’ patent) teaches a pump that has a separate single drug reservoir and a valve arrangement between the pump and the reservoir, however, the pump is between the catheter and the reservoir, and the intention of the invention is to provide an easily accessed refillable reservoir which can be located remotely from the pump, catheter, and the site of delivery. The '394 patent also describes, a two-step procedure which controls an arrangement of valves to realize filling and emptying the pumping chamber while decreasing the chance of the inadvertent introduction of the medication to the patient.
U.S. Pat App No 2002/0192751 A1 (the ‘751’ application) teaches methods and devices for modulating the rate of delivery of a drug by simply diverting a drug away from a single delivery pathway using a remotely controllable flow regulator. The flow regulator only affects the amount of drug going to a single catheter. The diverted drug can be sent into the systemic circulation or captured in a waste reservoir. However, the waste reservoir is different from a method which utilizes the diverted drug since the drug in the waste reservoir is not used at a later time. Further, the flow regulator does not address the existence of the drug which is already in the catheter, which is an issue when using multiple drugs since this drug must be eliminated (e.g., dispensed or purged) before a subsequent drug can be delivered.
While some prior art (e.g., US 2002/0156462) teaches using multiple reservoirs and multiple catheters or multiple lumens, each reservoir is uniquely connected to a single lumen or catheter. Accordingly, this prior art does not teach more than one drug to be output from each respective lumen or catheters. Prior art U.S. Pat. No. 6,471,688 enables drugs from multiple reservoirs to be dispensed from a single catheter to a single target region within the body of the patient, but does not teach how to deliver drugs to multiple target regions simultaneously. Prior art U.S. Pat. No. 6,471,688 also teaches a system which can allow for a single fluid from a single reservoir to be dispensed at multiple locations at the distal end of the catheter.
Drug delivery systems containing sensors and multiple pumps have been described which allow the delivery of drug to occur in response to a physiological event. For example, U.S. Pat. No. 6,066,163, describes an adaptive neurostimulation system which contains a reservoir infusion apparatus which stimulates the central nervous system with drugs in response to abnormal states which are sensed by one or more sensors. U.S. Pat. No. 5,062,841 discloses an insulin pump which can be used to pump insulin directly into the bloodstream in response to blood glucose levels. U.S. Pat. No. 5,433,701 discloses an active ocular pressure control device which includes a pump which is selectively operated in response to a control signal from a pressure sensor. However, these patents relate primarily to algorithms and methods of using the sensed data to control the pumping/drug delivery system and dispense an appropriate drug.
The prior art US 2003/0171738 (the '738 application) suggests continuously drawing upon fluids available from the implantee, in response to the immediate drug delivery needs of the implantee, which is disadvantageously dependent upon the availability of the implantee's fluids concurrent to the time of delivery. Further, a chamber is provided in the drug delivery device of the '738 application (see FIG. 3A), but this chamber only leads to a single catheter and the chamber has a fixed volume. Further, in FIG. 1a of the '738 application a carrier fluid from the reservoir is mixed with various drugs located in the catheter and somehow transmitted in a distributed fashion to several catheters, but in this case the drugs are undesirably mixed deterministically by the path of the flow of fluids over the “wells” of a microchip which contain drugs. Much of the technology described in the '738 patent relies on a catheter which contains a microchip drug delivery device. This microchip cannot contain much drug and is difficult to refill, and instead of being refilled is sometimes simply replaced, thereby requiring possibly complicated surgical intervention. Further, since drugs are dispensed by opening “wells”, a specific amount of drug is suddenly made available to the carrier fluid which transmits the drug to the implantee. It is not clear what might occur with the remainder of the drug which is contained in the catheter after the necessary amount has been delivered to the subject. In other words, when the amount of drug which is necessary for a specific drug regimen is known prior to implantation, then an appropriate amount of drug can be put into the “wells” of the microchip device. However, in the case where drug is delivered based upon sensed data and the object is, for example, to maintain a sensed parameter within certain limits, the use of a microchip incorporated into a catheter, as is described by the '738 application has an inability to provide a drug concentration and amount which is optimal to effect a desired change.
It is an object of the present invention to provide a drug delivery system and method to obviate or mitigate at least some of the above presented disadvantages.